In recent years, there has been known a technique of detecting a lane mark such as a white line on a road by capturing an image of the road along which a vehicle is traveling and processing the captured image with an imaging means such as a CCD camera mounted on the vehicle and performing vehicle control or provision of information to a driver on the basis of information on the lane (traffic lane) along which the vehicle is traveling recognized from a detection result. In this technical field, there has been suggested a technique for recognizing a lane accurately by performing image processing according to the situation of a road ahead based on the road information obtained from a GPS or map data or the like when recognizing the lane by image processing from the road image (refer to, for example, Japanese Patent Laid-Open No. Hei 11-72337/1999 (hereinafter, referred to as Patent Document 1) and Japanese Patent Laid-Open No. 2003-123058 (hereinafter, referred to as Patent Document 2). Moreover, there has been suggested a technique of performing the control or the provision of information by supplementing an image processing result with road information obtained from a GPS, map data, or the like (refer to, for example, Japanese Patent Laid-open No. 2002-92794 (hereinafter, referred to as Patent Document 3) and Japanese Patent Laid-Open No. 2003-205805 (hereinafter, referred to as Patent Document 4)).
The traffic lane recognizing device in Patent Document 1 includes an image information processing means which recognizes the positions of left and right white lines on the road ahead by processing image information from a camera, and a traffic lane estimating means which estimates the position and feature of the traffic lane and a positional relationship between the traffic lane and the subject vehicle from the white line position image information obtained by the image information processing means. The traffic lane recognizing device further includes a road condition determining means which determines whether there is a special particular road area (for example, a particular white line area having white lines in a striped pattern or zebra pattern) different from an area having normal white lines on the road ahead. The road condition determining means determines whether there is the particular road area on the road ahead while associating data on the particular road area stored in a ROM with vehicle position information obtained from a GPS. Although the image information processing means recognizes the midpoint of both edges of a white line as a position in the road width direction of the white line for a normal white line, a particular part of the white line area (an edge on the main line side of a recognizable white line area) is considered to be a position in the road width direction of the white line if the road condition determining means determines that there is the particular road area on the road ahead of the vehicle. Thereafter, the traffic lane estimating means estimates an area defined by the extracted left and right white lines on the road or an area defined by one of the extracted left and right white lines on the road and a previously recognized lane width as a traffic lane.
The traffic lane recognizing device in Patent Document 2 includes an image processing means which detects a traffic lane by processing a road image captured by a camera. The image processing means has a plurality of image processing algorithms different from each other according to a plurality of types of lane marks such as a white line, a raised marker, a post cone and so on. In this situation, the traffic lane recognizing device receives position information of the road along which the vehicle is currently traveling from a satellite by using a GPS receiving means and determines the type of lane marks on the road ahead along which the vehicle is currently traveling from a road map data file which stores lane mark types for respective roads. The traffic lane recognizing device selects an image processing algorithm suitable for the lane marks ahead out of the plurality of image processing algorithms and detects the traffic lane.
A warning device for a vehicle in Patent Document 3 includes a white line recognition system which recognizes left and right division lines (white lines) of the lane of the road along which the vehicle is traveling from the image obtained by a camera by image processing and a sensor group (vehicle speed sensors or the like) for use in obtaining vehicle behaviors. Moreover, the warning device for a vehicle includes a navigation system which obtains position information and road information on the road along which the vehicle is traveling by comparison with map data read from a CD-ROM on the basis of the position of a subject vehicle obtained from s GPS. The warning device for a vehicle issues a warning for a driver when predicting that the vehicle deviates from the lane on the basis of the left and right division lines of the recognized lane and vehicle behaviors obtained by the sensor group. In this situation, if the vehicle is traveling in a given road section (a road section determined to be a section where a false warning has been issued in the past) when determined from the obtained road information, the warning device for a vehicle changes a warning generation condition to a condition under which the warning is more difficult to be issued in comparison with other cases.
A vehicle driving support apparatus in Patent Document 4 includes a surroundings monitoring means which recognizes white lines or the like indicating a lane by processing an image ahead of a vehicle captured by a camera, and a driving support means which supports a driver's operation by a lane deviation warning control or the like on the basis of information from the surroundings monitoring means. Furthermore, the vehicle driving support apparatus includes a road condition recognizing means, which recognizes the road conditions (branch road or the like) of the road ahead of the vehicle from the current position of the vehicle obtained based on radio wave information from a plurality of satellites, map information stored in a storage medium such as a DVD-ROM, and road ahead information obtained by a road-vehicle communication from road infrastructure and which determines whether a problem will occur in driving support control according to the road ahead conditions. Then, the vehicle driving support apparatus previously provides a driver with information on the basis of information from the road condition recognizing means if reliability of the operation of the driving support means is projected to decrease.
In some cases, however, there may be an unpredictable skid mark or road repaired part on the road. In this situation, the existence of the skid mark or road repaired part cannot be known from previously stored road information. Moreover, it is difficult to recognize a lane accurately by image processing based on a road image due to the skid mark or road repaired part. Therefore, in this case, there is a problem that it is difficult to recognize the lane accurately even if the image processing is performed in consideration of the road ahead condition on the basis of the road information obtained from the GPS, map data, or the like, similarly to Patent Documents 1 and 2. Furthermore, in the above situation, even the device and apparatus in Patent Documents 3 and 4 find it hard to detect the lane by the image processing and cannot supplement the image processing result with the road information obtained from the GPS, map data, or the like, which leads to a problem that they cannot appropriately control the vehicle or provide the driver with information.